A self-correcting technique is one of cryptographic techniques (refer to Patent Literature 1 and Patent Literature 2, for example). The self-correcting technique is a technique for performing correct calculation at all time by using a calculator or a system which does not always output a correct calculation result (when a calculator which outputs a correct calculation result is used, a correct calculation result is outputted, and when a calculator which does not always output a correct result is used, a correct calculation result is obtained or a result representing that the calculation is impossible is obtained). For example, in a cloud-key management type decryption technique employing the self-correcting technique, a decryption capability provision device which holds a decryption key provides a decryption device only with information, by which the decryption device decrypts a cipher text, without providing the decryption device with the decryption key. The decryption device can always perform correct decryption calculation with this information.